Patients with well-documented chronic non-A, non-B hepatitis are being evaluated to determine the long-term natural history of this common form of chronic liver disease. A cohort of such patients are available to evaluate experimental therapies. Previous studies have shown that alpha interferon therapy has a short-term beneficial effect in approximately 50% of patients during treatment and that the beneficial response is sustained in approximately 20% after stopping interferon. A pilot study of ribavirin therapy has been conducted in 14 patients with chronic hepatitis C. Serum aminotransferases decreased during therapy in all patients and became normal in 5 (36%). Serum levels of HCV RNA also decreased significantly during therapy.